Green flashes at sunset are rare. Indeed, they were once thought mythological. Blue flashes are rarer still. On June 21st Göran Strand of Frösön, Sweden, saw them both in a single sunset:

"Tonight the weather was incredibly clear and fine, so I went out to photograph the sunset--and this was the result," says Strand. "The time interval between the first and last frames is 1 minute and 14 seconds."Green flashes are formed when the prismatic action of the atmosphere splits the setting sun into basic R-G-B colors. Temperature inversions create a mirage, magnifying the green into an eye-catching flash.Blues flashes are formed in the same way, but they are generally harder to see than green flashes, because blue flashes blend into the surrounding blue sky. When the air is exceptionally clear, however, the blue flash emerges.